WINETECH Technical Yearbook 2021

OENOLOGY RESEARCH | JULY 2021

Can yeast selection and fermentation temperature reduce the haze-forming proteins in Sauvignon blanc wine?

CARIEN COETZEE: Basic Wine, Stellenbosch KEYWORDS: Yeast selection, haze formation, Sauvignon blanc.

INTRODUCTION Pathogenesis-related (PR) proteins are the proteins responsible for hazes and sediments in wine. They are derived from the grape berry where the concentration can be affected by various factors such as cultivar, region and vintage, as well as viticultural and environmental fac­ tors (Monteiro et al ., 2003; Girbau & Stummer, 2008; Tian et al ., 2015; Ferreira et al ., 2001; Falconer et al ., 2010). The two principal groups of PR proteins responsible for protein instability in wine are thaumatin-like proteins (TLP) and

chitinases with the latter being mainly responsible for haze formation (Vincenzi et al ., 2011; Marangon et al ., 2011; Sauvage et al ., 2010; Tian et al ., 2017). The concentration of the PR proteins in wine is largely determined by their presence in pre-fermentation juice, which in turn is determined by the extraction of proteins from the grape berries. These proteins are resilient to low pH and proteolytic degradation and thus survive the winemaking process potential ly forming commercially unacceptable hazes in the wine (Ferreira et al ., 2001; Falconer

et al ., 2010; Feuillat, 2003; Linthorst & Van Loon, 1991). Some cultivars, such as Sauvignon blanc, generally have a higher risk of protein instability and the effect of oenological processes (other than targeted fining treatments) on these haze-forming proteins needs investigation.

A recent study aimed to elucidate the fate of the PR proteins during alcoholic fermentation of Sauvignon blanc and Chardonnay musts, specifically reporting the change in protein quantity and quality over time (Ndlovu et al ., 2019). The study specifically monitored the impact of factors

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